US2011/0181715 A1 describes a back-lit vision machine comprising a planar backlight located in a base of a coordinate measuring machine (CMM) for illuminating objects placed on the base. Backlit images are acquired by a CCD camera, these images processed by a computer to measure the location of edges of the object. Backlighting of non-planar parts facilitates the identification of the edges of an object.
For simple objects such apparatus detects edges of the object with the required accuracy. However, it has been found that for complex objects, such as objects comprising a series of overlapping walls or non-planar parts that cannot be uniformly illuminated by the backlight located in the base, edges of the object are not detected with the required accuracy.
WO94/01716 discloses a light emitting panel assembly that may be used as backlighting in a camera system used in inspection.
Stemmer Imaging Ltd provides Phlox® High Bright LED backlight panels suitable for use in machine vision situations.